Best bolt-on twins for RB26, ~300kw?

[joshuaho96]

Engine is out for a chassis refresh, I've been going in circles for the better part of a year now trying to figure out what turbos to select. Power goals are basically nothing to write home about, probably ~280-300 kW to the wheels on an honest australian dyno, wouldn't be surprised to get 280 kW on California 91 AKI (~95-96 RON AUS) but a good amount more if I go E85. To make emissions testing simpler it has to be a bolt-on twin turbo setup, doing anything else is going to be problematic. Most important to me is response at 3000-3500 RPM and the shape of the power curve, I don't want the turbo to choke the engine at 6000 RPM with 2000 RPM left to go or a turbo that takes until 4000 RPM to really get into the torque. In practice from what I've seen the R34 GT-R stock turbos are as responsive as it gets for stock mount twins, but I'm pretty sure those are ceramic turbines that can't take much more than 1 bar of boost or any mistreatment. I'm planning on running VCAM to try and compensate for the loss of the ceramic turbine. 

Should I get -7s? -9s? HKS' GTIII-SS turbos? Hypergear T25 high flow with BB CHRA? I've seen evidence that the GTIII-SS is really, really good for mid-range torque with VCAM but it still feels like a gamble, Garage Yoshida seems to suggest that it still feels lazy compared to -7s due to the bush bearing. -9s are supposedly just a little less responsive than -7s but with more favorable efficiency for high boost. GTIII-SS is supposed to be more response than -9s in the low/mid range, but boost tails off at high RPM from the small turbine so it can't sustain much more than 1.2 bar or so. The hope is with enough work the engine will feel more like a more modern engine in power delivery with VCAM and the right turbo choice instead of a more distinctly early 90s turbo power delivery.

[Murray_Calavera]

It sounds like your in California? 

If you wanted the car to be street legal and have a single turbo, what would that involve? I'm guessing it's not as simple as having the car certified by an engineer? (sorry if this is a dumb question, I'm over in Aussie land and not familiar with your processes)

[joshuaho96]

3 hours ago, Murray_Calavera said:

It sounds like your in California? 

If you wanted the car to be street legal and have a single turbo, what would that involve? I'm guessing it's not as simple as having the car certified by an engineer? (sorry if this is a dumb question, I'm over in Aussie land and not familiar with your processes)

You would have to get engineering certification for the kit, which basically requires you to do a test of the emissions of the car stock on the FTP-75 (ADR 27 cycle with an extra warm start repeat after a 600 second cooldown), US06, and SC03 drive cycles using 11.5 AUD/L certification fuel. This is easily like 4000-5000 USD. Then you have to modify the car with the specific part/kit you want to certify. You are not permitted to do things like use end user programmable ECUs, usually this means you're limited to the factory ECU. For R33 GT-Rs this is a huge headache because you can't easily remap the ECU, I don't even think you can buy new Hitachi H8/534s anymore. You must follow all of the relevant emissions regulations around PCV, evap control, and retain full functionality of the onboard diagnostics system from the original ECU. Once you've modified the car you then repeat the same emissions tests that were requested by the California Air Resources Board engineers and send that data to them. You also need to send detailed engineering drawings, specs, etc to them so they can understand exactly how the part is made and how it differs from the OEM part. You're only allowed a small deviation from stock emissions, basically to account for measurement error. In this case it would be the car post-emissions compliance for import. The cost of this is insane, it only makes sense if you can amortize over a bunch of different vehicles. You're probably easily looking at 10k USD per "item" if everything goes mostly right, there's no single vehicle certification process. 

In theory whatever the car has on it when it passes the original import emissions compliance testing/modification is "certified", but a condition of initial registration is another emissions inspection after you receive emissions compliance. You can't just take it to any emissions tester, it's a state "smog referee" that will look at the car and expect it to basically be stock. So if you roll up with a single turbo swap it doesn't matter if you've passed the nightmare FTP-75 test + evap test, they'll fail you and send you away when they see that the intake isn't stock and lacks a CARB EO number.

Personally I care about improving fuel efficiency and emissions where practical but I'm not rich enough to put down 10k just to prove that R35 injectors are in fact better atomizing than the OEM 440cc injectors. Or that a bolt-on turbo won't have any impact on emissions if constrained to the same mass flow rates as the OEM turbo on the OEM tune. Or that hot film MAFs are in fact better than the OEM hot wire MAFs. Or that a simple change to the twin turbo piping has no impact on emissions. The list honestly goes on and on. But the onus is on you to prove it through the same tests that the OEMs have to do to certify entire engine/transmission pairings.

Edited June 25, 2020 by joshuaho96

[GTSBoy]

Sounds like modifying a GTR in California is just one of those things that you simply should not consider.

[JGTC]

What mods are currently done to the car, and what mods have you already bought to go into the motor?

[joshuaho96]

7 minutes ago, JGTC said:

What mods are currently done to the car, and what mods have you already bought to go into the motor?

Engine is 100% stock, just noticing some oil on the compressor outlets so given the mileage of the car it's probably a good idea to replace the turbos. 

  

16 minutes ago, GTSBoy said:

Sounds like modifying a GTR in California is just one of those things that you simply should not consider.

Depends on your risk tolerance I suppose. Once the car is registered your average smog shop doesn't really know what they're looking at, just have to pass a 2500 rpm tail sniffer test.

Edited June 25, 2020 by joshuaho96

[Murray_Calavera]

Thanks for the detailed reply, really appreciate it!

I thought NSW was bad, I'd move states for sure if I had to deal with that. 

[GTSBoy]

55 minutes ago, Murray_Calavera said:

I'd move states for sure if I had to deal with that.

You can't. Moving out of California has been declared by the state of California to cause cancer.

[joshuaho96]

Laws aside, plenty of people running straight pipes, full decat, the works. So I’m not too worried about a bolt-on turbo getting noticed in an emissions check.

So should I do -7s? -9s? Is there some mythical BNR34 turbo that isn’t ceramic turbine?

[Robzilla32]

Just get -9s.

I get 360 awkw on e85 @ 20 psi with decent mods.

[Murray_Calavera]

5 hours ago, joshuaho96 said:

Laws aside, plenty of people running straight pipes, full decat, the works. So I’m not too worried about a bolt-on turbo getting noticed in an emissions check.

Well... what are your thoughts on a single turbo setup, having everything that can be anodised black (painted whatever) everything is black black black and very factory looking... once it's on e85 emissions are easy... 

What's the worst that could happen?

[joshuaho96]

8 hours ago, Robzilla32 said:

Just get -9s.

I get 360 awkw on e85 @ 20 psi with decent mods.

Maybe that's the answer in the end, feels like it at least.

5 hours ago, Murray_Calavera said:

Well... what are your thoughts on a single turbo setup, having everything that can be anodised black (painted whatever) everything is black black black and very factory looking... once it's on e85 emissions are easy... 

What's the worst that could happen?

Probably not wise, the other minor detail I didn't mention is that if you get pulled over by a cop that wants to give you a hard time you get sent back to the smog referee. Then it's a scramble to put everything back to what looks like stock. 

[GTSBoy]

3 hours ago, joshuaho96 said:

Then it's a scramble to put everything back to what looks like stock.

Sounds like every broke arse Skyline & Silvia owner over here for the last 25 years.

[joshuaho96]

5 hours ago, GTSBoy said:

Sounds like every broke arse Skyline & Silvia owner over here for the last 25 years.

Here I believe it mostly relates to the belief that Skylines are often used in street racing. These days the people who can afford to run a Skyline GT-R are not going to be racing them on the streets.

[JGTC]

-7s seem to peak around the 17-20psi mark, and -9 seem to breath around the 20-24psi mark (+2-3psi respectively for E85).  If you are going VCAM, -9s would be my choice to have the best balance of response and overall output.

My understanding is the HKS GTIII-SS is the updated version of the GT-SS which was based of the Garrett -9 unit.  The HKS unit would be my choice.

This was my mod-list to support my -9 build, it all adds up when you are starting from scratch and want to support the turbo set up as much as possible.

https://www.sau.com.au/forums/topic/93880-rb26-turbo-upgrade-all-dyno-results/page/31/?tab=comments#comment-7779972

Head / Turbo 

- Garrett 2860-9s - fitted with HKS oil feed restrictor banjo bolts

- Garrett 1bar actuators

- Tomei dump pipes

- Standard cast manifolds - Port matched to turbos

- Tomei Poncam Type A - lifter shim clearance within OE spec

- Jun adjustable cam gears (OR gears modified to be adjustable) - set to 0deg/0deg

ECU/AFMs

- Apexi Power FC

- Apexi analog boost controller

- Nismo AFMs

Cooling

- Plazmaman Pro Series 76mm intercooler

- Koyorad 48mm aluminium radiator

- Trust 13 row oil cooler with filer relocation kit

Exhaust / Intake

- Amuse R1 Titan Extra cat-back exhaust 90mm

- Apexi Super Catalyzer Cat - 80mm

- Mines Pro front pipe (2 x 70mm into 80mm)

- Nismo inlet piping

- OE Airbox with Nismo panel filter and snorkel

Ignition / Fuel

- Sard 650cc top-feed Injectors

- Splitfire coilpacks

- Wiring specialties coilpack harness

- Walbro 460lph fuel pump

- Denso iridium spark plugs

 

Edited June 26, 2020 by JGTC

[joshuaho96]

1 hour ago, JGTC said:

-7s seem to peak around the 17-20psi mark, and -9 seem to breath around the 20-24psi mark (+2-3psi respectively for E85).  If you are going VCAM, -9s would be my choice to have the best balance of response and overall output.

My understanding is the HKS GTIII-SS is the updated version of the GT-SS which was based of the Garrett -9 unit.  The HKS unit would be my choice.

This was my mod-list to support my -9 build, it all adds up when you are starting from scratch and want to support the turbo set up as much as possible.

https://www.sau.com.au/forums/topic/93880-rb26-turbo-upgrade-all-dyno-results/page/31/?tab=comments#comment-7779972

 

I'm definitely going to try and get all the supporting mods in to make sure the engine can perform well. I was thinking of getting the HKS GTIII-SS because of this chart:

I don't mind that at the end of the chart the GTIII-SS isn't much to write home about, what interests me is the pretty ridiculous amount of torque it puts out by 3300 RPM. But maybe this is just what happens when you're loading up the engine on the dyno from like 1500 RPM? But even -9s from the same tuner with VCAM Step 2 doesn't make ~213 whp by 3300 RPM, and it appears to also start from 1500 RPM:

Kansai Service put out a little blurb from their testing of the HKS GTIII-SS, personally I don't know how much stock I put into it but it suggests a decent mid-range bump, just not as good as what UP Garage is seeing:

But the GTIII-SS is a journal-bearing turbo and more than a few people have mentioned that it's not as responsive because of it. So not sure what to do here.

Edited June 26, 2020 by joshuaho96

[joshuaho96]

For anyone curious, I ended up going GT3-SS because the turbine a/r is 0.54 which is closer to the OEM turbine a/r of 0.49, multiple tuners that have tuned both GT3-SS and GT-SS in the US have mentioned that the GT3-SS trades power for low/mid torque compared to the GT-SS with a 0.64 turbine a/r. The goal has always been street-oriented so fingers crossed I don't regret paying way too much for a Civic Si turbo with an HKS stamp on it. I'll try and update with dyno results once I get it in.

[Matty George]

On 25/06/2020 at 9:02 PM, Robzilla32 said:

Just get -9s.

I get 360 awkw on e85 @ 20 psi with decent mods.

Man I’m putting -9’s on in 3 weeks and hoping for 300rwkw. 360 is awesome robzilla. What injectors and fuel pump?

[Robzilla32]

Raceworks 1000cc and Walbro 460lph

[TXSquirrel]

14 hours ago, joshuaho96 said:

fingers crossed I don't regret paying way too much for a Civic Si turbo with an HKS stamp on it.

A little too late my friend, you will be paying way too much for everything during the life of owning this car like the rest of us!

Edited June 30, 2020 by TXSquirrel